1. Field of the Invention
The present invention relates to a frame construction which comprises two frames, the first frame of which carries a machining tool, while the second frame carries functional devices for making the machining tool operate, and a machining device in which the frame construction is used in the machining work.
2. Description of the Prior Art
A laser machining device is widely used for cutting, welding, marking, and engraving workpieces such as a steel plate, a stainless steel plate, plywood, and a plastic plate by applying a laser beam to the workpiece. Recently, a high-power laser generator was developed by which workpieces such as thick steel plates can be cut or machined at a high speed. For this reason, a large-sized laser machining device is gradually being applied in plants in which members of a ship, a bridge and a steel structure are manufactured by machining relatively thicker plates.
In a laser machining device, it is necessary that a laser spot is moved on a workpiece with the diameter of the laser spot being maintained at the fixed value, in order to obtain a stable quality of manufactured goods. Namely, it is necessary to maintain the length of the light path of from a laser generator to a workpiece at a constant value.
For this reason, a laser machining device generally includes a frame composed of a saddle which is movably put on rails, and a cross girder which is disposed perpendicular to the rails, wherein a carriage moving transversely on the cross girder carries a laser torch and a laser generator.
On the other hand, a plasma machining device is also widely used in which a plasma arc is applied to a workpiece so that cutting, welding, gouging and other machining can be made. Generally, the plasma machining device comprises a frame which carries a plasma torch, while a plasma power source is arranged on a floor, wherein the plasma torch and the plasma power source are connected through a cabtire cable for high power.
It is also known that when workpieces such as steel plates, and stainless steel plates are cut by using a plasma torch, a large amount of dust is generated with cutting. Therefore, a machining device with plasma torch is provided with a dust collecting equipment. It is also known that fumes including dust is generated when steel plates or steel plates on which antitrust paint is coated is cut with a gas torch.
It is known that a plasma machining device provided with dust collecting equipment in which a main body composed of a suction fan, a dust separator and others is arranged on a floor, while a duct is arranged parallel to rails on which a frame carrying a plasma runs, wherein an opening of the duct is opposed to the plasma torch while the frame is moved. Since in the dust collecting equipment, the main body is secured on the floor, together with the frame being kept off from the main body, the length of the extended part of the duct is increased, and the a suction resistance is increased while the dust collecting efficiency is lowered.
For this reason, the main body of the dust collecting equipment is mounted on a frame of the machining device, wherein an opening of the duct connected with the main body is opposed to the plasma torch. In the dust collecting equipment, a length of extended part of duct can be maintained at the fixed value, irrespective of the position of the frame on rails, so that the stable dust collecting efficiency can be exerted. However, the weight of the laser generator is increased, together with an increase in the power of the laser generator, so that the total weight of the machining device provided with the high-power laser generator amounts to 5 tons to 8 tons. Further, in the plasma machining device, it is required that a plurality of plasma torches are mounted on the frame. However, in such a machining device, the force required for drawing cabtire cables is increased, and drawing of the cables becomes intricate. In order to avoid this problem, a power source is mounted on the frame, by which the weight of the machining device is increased.
Further, in a gas machining device, it is also required that a plurality of gas torches be mounted on a frame, by which the weight of the machining device is increased together with an increase in functional devices such as valves acting to open or block passage of preheating oxygen, fuel gas, and cutting oxygen, pressure control valves, and a backfire preventive device.
Further, in a machining device provided with dust collecting equipment on a frame, there is a in problem that the dust collecting equipment provided on the frame increases the load applied to the frame and the high rigidity of the frame required corresponding to the increased load increases the empty weight of the frame. Further, there is a problem that together with an increase in the weight of the frame, the force of inertia is increased, and so a rise time of from the starting time point of the machining process to a time point when the speed of the frame reaches the cutting speed is increased.
Speed control of tools such as laser torches, plasma torches, and gas torches become difficult, together with an increase in the weight of the machining device. Particularly in laser machining or plasma machining, it is required that the moving speed of a torch reaches the machining speed, which is set according to the power of the laser generator or a plasma electric current, as quickly as possible, wherein when the moving speed of the torch and the machining speed is unbalanced, the impossibility or inferiority of the machining is generated so that the quality of the product cannot be maintained.
Particularly, in a NC machining device or copying machining device, considering that an increase in the weight of the machining device accompanies an increase in the force of inertia thereof, when the cutting direction is changed over, it is regarded that a long section is provided in front of the turning point of a cutting torch so that the cutting speed can be decreased in the section. In this case, excessive heat is given to a workpiece in the section, so that the quality of the cut surface is much worse.
In order to avoid the above-mentioned problems, a high-power drive motor is needed for increasing the a machining speed from a state of stop to the given machining speed in a short period time, therefore, the drive motor and conductor means are required to be large-sized. Further, the large-sized motor and conductor means make the machining speed change in a short time according to the drive signal inputted to the drive motor, when the direction of the cutting torch is changed over at a corner part which has a shape with a right-angled corner, or when the speed of the machining device is decreased from the machining speed to a state of stop, and accordingly a brake with immerse braking force is needed.
However, when a high-power drive device and a brake with immerse braking force are used, considerable shock is applied to a machining device every time the machining speed is changed. Therefore, the strength of a drive shaft and a frame must be increased so that the weight of the machining device is significantly increased. Further, in order to control the machining speed without the shock being applied, a runaway section is preferably provided in front of a point where the desired speed is attained, and in the runaway section the machining speed gradually rises or falls. However, in this case, the quality of the product deteriorates in the runaway section.
Further, generated when the machining speed is changed, the shock transforms into the frequency of torch which exerts a bad influence on the machining accuracy. In this case, substantial change in the speed is generated near a turning point of the machining direction. Thus, the positioning accuracy of the torch becomes worse a braking force and the drive force acting on the frame, and a poor influence is exerted on the quality of the machined surface and the dimensional accuracy.